System of operation for alternating-current motors and generators.



w. 000mmnnuume 0111mm MOTORS AND GENERATORS.

Patented Dec.'6, 1910.

SYSTEM OF OPERATION FOB ALT nrucumx FILED swans, 1907'.

WITNESSES: INVENTOR ATTORNEY ZZQM I UNITED s'rarnslatrnnr OFFICE.

WILLIAM coornn, or rrrrsnm'ne, PENNSYLVANIA, assrcnon T WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION or PENNSYLVANIA.

SYSTEM OF OPERATION FOR ALTERNATING-CURR ENT MQTORS AND GENERATORS;

Specification of Letters Patent. i

Patented Dec. 6, 1910.

' Application filed September 3, 1907. Serial No. 391,225.

To all whom it may concern: Be it known that I, WILLIAM COOPER, a

citizen of the United States, and a resident .of Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Systems of Operation for Alternating-Current Motors and Generators, of which the following is a specification. My invention relates to dynamo-electric machines of the commutator type, and to systems of operation therefor.

may be convertedinto braking generators,

in order that the potential energy possessed by the vehicle, when coastmg or stoppin may be transformed into electrical energy and supplied to the distributing circuit.

If two or more alternating current motors of the connmitatortype are employed upon a vehicle, the above mentioned result may be effected by utilizing one of the motors as an exciter for the field magnet windings of the remaining motors the armaturcs of which are connected to the distributing circuit or line, the field magnet winding of the eXciter being supplied from the line.

As motors are usually constructed, the

ohmic resistances of the field magnet windy tings are very low and, therefore, the cur rents in the said windings and, consequently, also the generated electromotive forces are approximately 90 out of phase with the electromotive forces app ied to the' field magnet windings. Since the machines in the system are connected in tandem, the electromotive forces of the armatures that are connected to the line are substantially in phase with the electromotiv'e force of the line. However, by reason of the inductance unavoidably present in the armature circuit,

- According to the present'invention, the current supplied to the line may be caused toagree in phase with the line electromotive force, or to lead 01' lag behind the same, as desired, by adjusting the phase of the electromotive force applied to the field magnet windings of the generators with respect to the ,line eleetromotive force, the adjustment being effected by inserting an ohmic resistance, either in circuit with the field magnet winding of the exc'iter, or "in the armature circuit of the exciter.

My invention is illustrated in the accompanying drawings, Figure L of which is a diagrammatic view of the arrangement of the circuits when operating the machines as motors. F 1g, 2 1s a diagrammatic view of one arrangement of the circuits when oper;

ating the; machines as generators. Figs. 3 and 4 are vector diagrams illustrating phase relations of the currents and electromotive t'orces when operating the machines as generators. Fig. 5 is. a diagrammatic View of another arrangement of the circuits for op-. erating the machines as generators. Fig. 6 is a vector diagram illustrating the phase relations of the currents and electromotive forces in the system shown in Fig. 5.

1n the system shown in Fig. 1, two dynamorlectric machines of the commutator type ot construction having field magnet W1I1dings 1 and ,2, armatures 3 and i and com pensating windings 3 and 4 adjacent to and inseries with the armatures, are connected in parallel relation between suitable points in a transformer winding 5, that-is connected between conductors 6 and 7 of a suitable distributing circuit or line. The lield magnet and armature windin s of each machine ai'feconnected in series relation for operating the machines as motors, and the speed of operation may be varied by ad'ush' ing the active length of the portion 0 the transformer winding 5 that is included in circuit with the motors, a suitable means for ell'ecting this result, without causing injury to the controlling devices, being set forth in Patent No. 797,060, granted August 15, 1905, to the lVestinghouse Electric & Manufad turin g Company as assignee ofRay P. Jackson. and in Batent No. 834,525, granted October 30, 1906 to the Vl estinghouse Elec 7 external devices vehicle the transformer 5 being carried by the vehicle and the line conductors (3 and 7 being the trolley conductor and track rail, respectively, of the railway system. It will be understood, however. that the invention may be embodied in other than rail'way systems whenever it is found desirable to do so.

In order that the machines may be operated as generators when stopping the vehicle, or when it is coasting, or when descending a grade-for the purpose of assisting in braking and for converting the potential energy of the vehicle into electrical energy to be returned to the distributing circuit or line, field magnet winding 1 is connected to, and is supplied with exciting current from, the transformer winding 5, while armature 3 of the same machine supplies exciting current to field magnet winding 2 of the .other machine, the armature of which is connected between suitable points of and supplies current to, the transformer winding \Vhile, with such an arrangement of circuits, the electromotive force generated in the armature 4 will be substantially in phase with the clectromotive force of the transformer winding 5, since the electromotive force applied to each field magnet winding of the tandem-connected machines will be substantially 9O out of phase with electromotive forces generated in the corresponding armatures. the current in the circuit of the armature 4. i. 6., the curren returned to the line through the transformer winding 5, will be considerably out of phase with the electromotive force of the transformer on account of the inductance of the armature. This will be readily understood from a consideration of the vector 'liagram of Fig. 3. In Fig. 3, and in the succeeding vector diagram, E value, the electromotire forcesof the transformer winding .3 between the terminals of the armature i when the circuits are arranged as in Fig. 2, for operation of the machines as generators. E represents the electromotive force applied to the field magnetwinding 1, which is in phase with the transformer electromotive force 1,, if no are included in the circuit with the field magnet winding. L, represents the current in the field magnet winding lot the exciter generator. This current lags approximately 90 behind the applied electromotive force E because, as such machines are usually constructed, the ohmic resistance of the field magnet winding is substantially negligible in comparison with the inductive resistance. It also represents the exciter field fiux. 13 represents the electromotive force generated by the exciter armature 3 which is in phase with the field flux. As here represented. however, it is 10 out of phase with the field current I the armature connections being consider d motive force 13.. Since the amount of returned to the line is equal to the comrepresents, in phase and as reversed. E. represents the component of the generated electromotive force. E. re quired to overconnr the impedance of the exciter armature 3. l represents the romponent of the generated elecu'oimitirc tort-c E applied to the field magnet winding 2 ,of the generator that supplies current to the line. I representsthc current in the field magnet winding 2 and also the tiux produced thereby. lt lags approximately 0* behind the electromotive t'orce F ecause of the low ohmic and high inductive resistance of the field winding. 15,, reprw sents the electromotive force generated in the armature 4, it being in phase with the field current I' 1 represents the impedance drop -in the circuit of the armature at. I represents the current in the circuit of the armature .4 or that supplied to the line. its phase is determined. with reference to the electromotive force E by the relation of the ohmic to the inductive resistances "in the armature circuit,'and because of the inductire resistance, it lags behind the said electromotive force, and is also very much out of phase with the transformer electropower ponent of the tlll't'tll" that is in ohase with the transformer el ctromotive force. and the said electromotive force. it is evident that the maximum amountof power for a give-ft current will be returned to the line when the current I and the transformer electromotive force E. agree in phase.

In order to cause the current I to agree in phase with the transformer electromotive force F... I proposeto insert a resistance 9 in series with the field magnet winding 1 of the exciter generator 'in order to shiftthc phase of the electromotive force applied to the field magnet winding 2 with respect to the transformer electromotive forcel h. The efiect of placingthe resistance 9 in series with the field winding 1 may be understood from a consideration of the vector diagram of Fig. -l. E. represents the electromotive force applied to the resistance S). and it is in phase with-the current L, in the circuit. The electromotive force In. applied to the field winding 1 is. therefore. no longer in phase with the transformer electromotive force 15., as represcntcd in Fig. 3, but the transformer electrornotive force I. is the resultant of the elcctromotive forces E and E The remainder of the diagram of Fig. 4 is constructed in the same manner as the diagram of Fig. and the same reference characters are employed. It will be observed that the electromotive force E applied to the field magnet winding 2 and. consequently. also the current I in the said winding and the electromotiveforce E generated in the armature core are so shifted in phase with respect to the transformer electromotive force E, that the current I in the circuit of the armature 4: is brought into base with the transformer electromotive fibrce E,. While this is usually the 'most desirable condition under which toreturn power to the .line, it may become desirable, in certain instances, to cause the current I to lead or even lag behind the transforrner electrom'otive" force E and this result ma be readily effected, as will be at once an erstood from'a'consideration of the diagrams of Figs. 3 and 4, by adjusting the value of the resistance 9.

The desired phase relations may also be secured by insertin a resistance 10 in the circuit including 51c exciter armature 3 and the generator field winding 2, as will be understood from a consideration of the vector diagram of Fig. 6.- In this dia gram, as well as in the other vector diagrams, E represents the resistance component of the electromotive force E required to overcome .the impedance other than that of the field magnet winding 2 in .circuit with the exciter armature 3. By increasing the value of the resistance component E,, as is done in Fig. 5, and as represented in Fi 6, the phaseof the electromotive force applied to the generator field winding 2 may be shifted with re? spect to the electromotive force E gener-' 'ated by the exciter armature 3. This, in turn, serves to shift the phase of the electromotlve force E generated by the armature .4, and the current I is thereby brought into phase with the transformer electromotive force E,, or it may be caused to bear other desired phase relations with respect thereto by properly adjusting the value ofthe resistance 10.

I claim as m invention:

1. .The combination with 'an alternating current distributing circuit, and a generator connected thereto, of an exciter that supplies the field magnet winding of the gen-' erator having its field magnet winding connected to the distributing circuit, and means interposed between the connections to the distributing circuit for adjusting the phase of the current supplied to the circuit with respect to the electromotive force of the circuit.

2. The combination with an alternating,

current distributing circuit, and a generator connected thereto, of an exciter that supplies the field magnet winding of the generator having its field magnet winding connected to the distributing circuit, and means interposed between the connections to the distributing circuit for causing the current supplied to the circuit to agree approximately in phase with the electromotive force of the circuit.

3. The combination with alternating current distributing circuit, and a generator connected thereto, of an exciter that supplies the field ma net winding of the gen,- erator havingits nected to the distributing circuit, and a variable resistance interposed in circ'uitwith one of said field ma' "et windings for adeld magnet winding con-X justing the phase of t e-current supplied to the distributingcircuit with respect to the electromotive force of the circuit.

4.. The combination with an alternating current distributing circuit, and a generator connected thereto, of an exciter that supplies the field ma et winding of the gencrator having its eld magnet winding connected to the distributing circuit, and a resistance interposed in c rcuitwith one of said field magnet windings for-causing the current supplied to the distributingcircu t toagree approximately in phase with the electromotive force of the circuit.

5. The combination with an alternating current distribQting circuit, and a generator that supplies current thereto, an exciter that supplies the field ma net winding ofthe generator having. its eld magnet winding connected to the distributing circuit, and means disposed in the circuit of the field magnet windin ofthe exciter 'for adjusting the base of t e current supplied to the circuit with respect to the electromotive force of the circuit.

6. The combination .with an alternating current distributing circuit, and a generator 1 that supplies current thereto, an exciter that supplies'the field magnet winding of the generator having its field magnet winding connected to the distributing circuit, and a resistance disposed in the circuit'of the field dynamo-electric machine with respect to the electromotive force of the distributing circuit.

In testimony whereof, I have hereunto subscribed my name this 24th'day of August,

. WILLIAM COOPER. WVitnesses:

HOWARD L. BEACH, BIRNEY Hmns, 

